The present invention relates to a therapeutic medical compression garment, a knitted fabric and a method of forming a knitted fabric. More particularly, the present invention relates to a therapeutic compression garment with structural features on the inner surface to contact the skin of the wearer. These structures increase the resistance to slipping down the limb that is characteristic of prior art hosiery products. For purposes of illustration the invention disclosed in this application refers to hosiery products used on the leg or portions of the length of the leg, and the term hosiery product, hosiery garment and stocking are used interchangeably.
Therapeutic medical compression garments are used to assist in the management of various venous and lymphatic disorders, particularly in the lower extremities of the body. The purpose of the stocking is to minimize or eliminate the effects of elevated venous pressures caused by gravity or disease processes by reducing the tendency of blood to pool in the lower extremities. This type of stocking may also be applied to inactive, bedridden individuals to reduce the occurrence of clot formation in the lower extremities that can travel to the heart or lungs where a thromboembolism may develop. This type of stocking functions by maintaining blood flow and typically has a graduated pressure profile to effect a predetermined compression of the leg sufficient to force blood upwardly out of the extremities and into circulation. External circumferential counter pressure maintains the venous and lymphatic pressures at a more normal level in the extremity, thus assisting the movement of venous blood and lymph from the extremity. Another important effect of compression is the reduction of venous volume that leads to an increase of venous flow velocity. Edema reduction and prevention is the goal in patients with chronic venous insufficiency, lymphedema, and other edema causing conditions. Subcutaneous pressures increase with elastic compression. This rise in subcutaneous tissue pressure acts to counter transcapillary forces, which favor leakage of fluid out of the capillary.
There are a variety of known therapeutic medical compression garments. However, known therapeutic stockings have a tendency to slip down the leg of the wearer, thereby detracting from the benefits of the stocking. An example of a therapeutic stocking is described in U.S. Pat. No. 3,975,929 to Fregeolle which describes a thigh length anti-embolism stocking made with alternating courses of covered spandex yarn knitted on a circular hosiery knitting machine. The stocking described in Fregeolle shows a turned welt around a portion of the top of the stocking and a narrow elastic band stitched to the upper portion of the stocking. The inner face of the elastic band is provided with beads or rows of frictional gripping material that aid in supporting the upper end of the stocking on the leg of the wearer by frictionally engaging the leg.
Another example of a therapeutic stocking is described in U.S. Pat. No. 3,874,001 to Patience, et al., which discloses a full length stocking having a foot and leg portion made from elastic. A narrow band of non-slip elastomeric webbing material is sewn onto the upper end of the leg portion by over stitching. The particular stitching used is said to provide for adequate movement of the knitting loops relative to each other to insure the deformation of the stocking as it is worn.
U.S. Pat. No. 3,983,870 to Herbert, et al. discloses a slip-resistant support for limbs, especially a medical stocking. Herbert, et al. addresses the slip problem by coating 20 to 30 percent of the inner surface of the knitted thread with a non-adhesive, non-continuous, relatively soft elastomeric polymeric material with a high coefficient of friction to skin so as to provide a non-occlusive slip resistant surface capable of maintaining the support in place on the limb of the body.
Yet another type of anti-embolism stocking is disclosed in U.S. Pat. No. 3,728,875 to Hartigan, et al. This stocking is knitted on a circular hosiery knitting machine and the upper portion is slit downwardly in a walewise direction and a wedge-shaped insert of soft elastic fabric is sewn into the slit to increase the circumference of the upper end of the stocking. In stockings of this type, the sewing of the wedge increases the cost of production. The insert is formed of a different compressive fabric than the remaining portion of the upper end of the stocking so that the portion of the leg covered by the insert does not receive the same compressive force as applied to the remaining portion of the leg of the wearer. The stocking also has a partial elastic retention band made with a corrugated anti-slip inner surface of urethane elastomer sewn to the upper narrow welt of the stocking and projecting above the stocking welt so that its top forms a continuous line with the top of the insert.
Therefore, it is desirable to form anti-slip portions in compression garments that on the one hand keep the garment in position on the wearer's limb and on the other hand are comfortable to wear. In order to achieve a high degree of slip resistance between the compression garment and the respective body portion, it is known to incorporate so called “friction yarns” into the knitted structure that have a high coefficient of friction with the human skin. The high slip resistance reduces the tendency of the garment to slide along the body, and thus it is not necessary that the garment apply pressures exceeding a limit acceptable for the wearer.
Publication WO 2011/116952 A1 (“Clemendot”) discloses a garment portion formed entirely of a high-friction yarn incorporated into a compression garment. It is a disadvantage of this knitted structure that the surface of the anti-slip zone facing away from the user's body is also entirely formed of high-friction yarn. This outer surface can cause a garment worn on top of the compression garment to cling to the underlying compression garment and be prevented from easily sliding relative to the compression garment as the wearer moves, causing discomfort to the wearer.
A more recent compression stocking is disclosed in U.S. Pat. No. 6,871,516 to Peeler et al. The stocking disclosed in Peeler is a therapeutic medical compression garment with an integrally knit anti-slip portion located in the upper area of the garment. The garment functions by placing high friction yarns directly next to the wearer's skin. The high-friction characteristics result from the texture formed on the inner side of the garment during the knitting process.
Thus, while improvements have been made to the anti-slip properties of anti-embolism garments, there remains a need for an effective, inexpensive therapeutic medical compression garment that will resist slipping down the leg of the wearer.